The present invention relates to a vaporizer for vacuum deposition installations, particularly electron-beam vaporizing means, having at least one crucible and a plurality of crucible-receiving recesses movable into a vaporizing position, and having a vapor-conducting device and a shutter for interrupting the flow of vapor.
The "vapor rays" emanating from vaporizers are relatively diffuse and are propagated in such a form that it is impossible to avoid applying a vapor deposit to surfaces other than those of the substrate intended to be coated. It is known to concentrate or deflect vapor rays by means of vapor-deflecting devices, reflectors, etc., which are firmly connected to the vaporizer concerned. In such arrangements no problem arises if the vapor condenses on the conducting device. Also, vapor condensate can be prevented from forming by keeping the vapor-conducting device at a suitable temperature level.
Difficulties arise, however, when use is made of what are known as multi-dish crucibles from which are vaporized different substances which should not contaminate each other. This need arises, for example, in the vapor-deposition of what are called interference-layer systems consisting of individual layers having different refractive indices and as used in optical products, or during the vapor deposition of alternately conductive and insulating coatings in the cae of electronic products.
In the case of a vaporizer comprising a multi-dish crucible but no conducting device, it is known, for the purpose of preventing mutual contamination of the individual deposition substances, to provide a screen plate above the crucible, which screen plate is provided with an opening at that point where one of the crucible-receiving recesses is located at the vaporizing position, whereas the projection of the vaporizing plate covers the remaining recesses. Apart from there being no vapor-conducting devices in this system, mutual contamination of the vaporization substances cannot be avoided, since because of the displaceability of the multidish crucible, a gap, albeit narrow, is present between the crucible and the screen plate, and material can pass through this gap to the adjacent substance and can form a vapor deposit thereon. Furthermore, part of the vapor condenses on the screen plate and can pass into the adjacent substance. A further risk of mutual contamination arises as a result of part of the vapor inevitably condensing on the shutter which can be swung into the vapor stream. After the coating on the shutter has acquired a relatively large thickness, it begins to flake off, and the possibility of particles of one or more substances falling into the crucible dish containing another substance cannot be precluded.